The present invention relates to knee replacement surgery, and in particular relates to preparation of the distal end of a patient's femur to receive a part of a prosthetic knee joint.
Surgery to replace an entire knee joint has become relatively common in recent years, and various types of prosthetic knee joints have been designed. Each replacement knee joint requires preparation of the femur and the tibia of the patient to receive portions of the prosthetic joint that operate together to provide mobility approaching that of the patient's natural knee joint. For a replacement knee to operate optimally and for the patient to be able to move with a natural gait, the prosthetic knee joint parts must be installed in precisely the right positions and alignment.
A portion of the distal end of the femur must be removed to provide a seat for the femoral prosthetic part. According to earlier procedures for location of the portions of a prosthetic knee joint, an intramedullary rod is installed in the femur being prepared, and the proper location and orientation of a saw guide is referred to such an intramedullary rod, as taught, for example, by Cripe et al., U.S. Pat. No. 6,193,723.
Dunn et al, U.S. Pat. No. 4,759,350 discloses another cutting guide located on a patient's femur through the use of an intramedullary rod to guide in cutting away portions of the distal end of a femur in order to receive a prosthetic knee joint.
Many patents, including McNulty et al., U.S. Pat. No. 5,688,279, D'Antonio, U.S. Pat. No. 5,810,831, Dunn et al., U.S. Pat. No. 4,759,350, Lackey, U.S. Pat. No. 5,053,037, Hodge, U.S. Pat. No. 5,486,178, Samuelson et al., U.S. Pat. No. 5,611,802, Marik et al., U.S. Pat. No. 5,417,694, and Booth, Jr. et al., U.S. Pat. No. 5,688,280, disclose various devices intended to aid surgeons in properly locating and orienting cuts which must be made to prepare the distal end of the femur to receive the relevant portion of an artificial knee joint.
Recent practice, however, has involved the use of infrared measuring devices communicating with a computer in a navigation system to determine the proper orientation of the femur and tibia with respect to each other and thus to determine the required locations for the portions of a prosthetic knee joint. It has become possible to utilize information determined through use of such an infrared navigating system to locate saw guides used to make an initial cut as part of preparing the distal end of the femur.
For example, the femoral portion of a prosthetic knee joint must be properly aligned with the central longitudinal axis of the femur and must also be oriented at the proper varus/valgus angle with respect to the longitudinal axis of the femur. It must also be mounted in the correct position of rotation about the hinge axis of the prosthetic knee joint to provide for the correct range of articulation.
It is desired, then, to provide a distal femoral cutting guide that can be used either with an intramedullary rod or with the assistance of infrared or other computer-aided navigation methods to locate a guide block properly for making a transverse cut across the condyles of the femur.